Droplet imaging instrument metrology instrument for icing condition detection

摘要

An instrument for measuring water droplets is described and constructed. It is designed to measure the volume concentration and the size distribution of droplets in order to detect icing conditions in a natural fog. The instrument works by shadowgraph imaging, with a collimated blue LED as background illumination. We show how to use a reference object to obtain a calibration of the droplet size and the measurement volume. These properties are derived from a measurement of the object's shadow intensity and its edge second derivative. From the size of every measured droplet and its expected detection volume, a measure of the liquid water content (LWC) and the median volume diameter (MVD) can be estimated. The instrument can be used for continuous measurement in a remote weather-exposed location and is tested in a small environment chamber. We also describe this chamber and how we can change the LWC using an ultrasonic fog generator and a fan.